Reduction-Controlled Viologen in Bisolvent as an Environmentally Stable n-Type Dopant for Carbon Nanotubes

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• 作者：Soo Min Kim ; Jin Ho Jang ; Ki Kang Kim ; Hyeon Ki Park ; Jung Jun Bae ; Woo Jong Yu ; Il Ha Lee ; Gunn Kim ; Duong Dinh Loc ; Un Jeong Kim ; Eun-Hong Lee ; Hyeon-Jin Shin ; Jae-Young Choi ; Young Hee Lee
• 刊名：Journal of the American Chemical Society
• 出版年：2009
• 出版时间：January 14, 2009
• 年：2009
• 卷：131
• 期：1
• 页码：327-331
• 全文大小：347K
• 年卷期：v.131,no.1(January 14, 2009)
• ISSN：1520-5126

文摘

Various viologens have been used to control the doping of single-walled carbon nanotubes (SWCNTs) via direct redox reactions. A new method of extracting neutral viologen (V⁰) was introduced using a biphase of toluene and viologen-dissolved water. A reductant of sodium borohydride transferred positively charged viologen (V²⁺) into V⁰, where the reduced V⁰ was separated into toluene with high separation yield. This separated V⁰ solution was dropped on carbon nanotube transistors to investigate the doping effect of CNTs. With a viologen concentration of 3 mM, all the p-type CNT transistors were converted to n-type with improved on/off ratios. This was achieved by donating electrons spontaneously to CNTs from neutral V⁰, leaving energetically stable V²⁺ on the nanotube surface again. The doped CNTs were stable in water due to the presence of hydrophobic V⁰ at the outermost CNT transistors, which may act as a protecting layer to prevent further oxidation from water.